Glass furnace charging



Feb- 12, l952 J. B. wHlTMoRE ET AL 2,585,607

GLASS FURNACE CHARGING 5 Sheets-Sheet l Filed June 25, 1941 INVENTOR J5` W//7M0/?E" E' /9 NEM/COMBL- BY mum ATTORNEY PMT/NUM CHP Feb- 12, 1952J. B. WHITMORE ETAL 2,585,607

GLASS FURNACE CHARGING Filed June 25, 1941 5 Sheets-Sheet 2 W wwwATTORNEY Feb- 12, 1952 J. B. WHITMORE ETAL 2,585,607

GLASS FURNCE CHARGING INVENTORS JT Bt MHH-0K5 177 F fuffa/w55.

AMMWWL v ro Fmr Maf-wr zeig ATTORNEY Patented Feb. 12, 195:.-

GLASS FURNACE CHABGING James B. Whitmore, Bloomiield, and Frank A.

Newcombe, Nutley, N. J., assignorsto Westinghouse Electric Corporation,East Pittsburgh, Pa., a corporation of Pennsylvania Application June z5,1941, semi No. seats:

'I Claims. 1 This invention relates to apparatus for supplying moltenglass, and more particularly to means for controlling the feeding of rawmaterial to glass-melting furnaces.

The principal object of our invention, generally 1 considered, is toprovide for automatically maintaining the level of the liquid materialin furnaces, and especially glass-melting furnaces.

Another object of our invention is the provision of a furnace chargeroperable through a glow tube or thyratron, in accordance with the levelof liquid in the furnace, the operation of said control apparatus beingdetermined by the resistance between a submerged electrode and onewater-cooled which just touches or breaks contact with the glass.

A further object of our invention is the provision of a controller ortimer which determines the proportion of each of short intervals whichare charging when the level of molten glass or other material in acontrolled furnace drops below an electrode, thereby calling foroperation of the charger.

A still further object of our invention is the provision of a hoist fora batch box to load raw.

material, as the need arises, in a bin from which a. furnace may becharged.

An additional object of our invention is the.

l is of durable material, long life and uniformity in operation isassured.

A further object of our invention is the provision of-apparatus forautomatically maintaining the normal or a predetermined molten glasslevel in a glass melting furnace and devices for insuring safe operationof said apparatus and furnace.

Other objects and advantages of the invention, relating to theparticular arrangement and construction of the various parts, willbecome apparent as the description proceeds.

Referring to the drawings illustrating our invention; W

Figure l is a side elevational view, partly in vertical section, of aglass-melting furnace and associated hoisting and charging apparatusembodying our invention.

Figure 2 is an enlarged fragmentary vertical sectional view through thewater-cooled electrode shown ln Figure 1, water supply pipes being shownpartly in elevation.

Figure 3 is a fragmentary view corresponding to Figure 2, but showing amodification.

Figure 4 is a horizontal sectional view of the hoisting and chargingapparatus, as shown in Figure 1, but separated from the furnace, andillustrated in the position where the batch box hoist has just raisedsufficiently to engage and start to lift the operators platformtherewith.

Figure 5 is a view corresponding to Figure 4, but showing a subsequentposition in which the batch box hoist and operators platiorm have risenpart way towards the top of the raw material bin.

Figure 6 is a view corresponding to Figure 4, but showing the nalposition in which the batch box hoist and operators platform havereached the top of their travel with respect to the bin, and the slidingdoor of the bin has been opened allowing the batch box to be moved fromthe dotted position to the full line position for subsequent dumping bythe door releasing vthe operating lever or pawl, to discharge thematerial into the bin as represented.

Figure 7 is an enlarged sectionalr view of the batch box showing how thedumping doors are operated.

Figure 8 is a front elevational view of the interval timer preferablyemployed for controlling the operation of the charging mechanism.

Figure 9 is a vertical sectional view on the line IX-IX of Figure 8 inthe direction of the arrows.

Figure 10 is a vertical sectional view on the line X-X of Figure 9 inthe direction of the arrows.

Figure 11 is a wiring diagram for the apparatus illustrated in thepreceding figures.

Prior to our invention, glass-melting furnaces of the assignee 'of thepresent application were charged by hand, usually at intervals ofonehalf hour. During such charging periods, lasting from two to threeminutes, the furnace was shut down. Shutting down the furnace every halfhour resulted in an interior temperature drop of several hundreddegrees, causing considerable trouble in maintaining a. uniform glasstemperature, something that is of vital importance, especially in makingbases as described and claimed in Patent No. 2,116,450, dated May 3,1938, and owned by said assignee.

Due to the drop in furnace pressure, caused by shutting down the furnacewhile being charged, the glass flow decreased to such an extent that themachine had to be slowed down ten to fifteen per cent and remain at suchreduced speed throughout the charging period. Such decrease in speedresulted in an average of 12% productioniloss for five minutes eachhour, or an average loss of production of 1%. In accordance with theautomatic charging apparatus which will now be described, feeding batchmaterial to the furnace while the latter is in operation, eliminates theproduction loss.

Broadly speaking, the apparatus which embodies our invention, and isabout to be described, comprises:

(1) Special electrodes and controller associated with a furnace to becontrolled.

(2) A charging and driving unit.

(3) A hoist and batch box.

(4) An interval timer, and

(5) An electrical control circuit.

Referring to the drawings in detail, like parts being designated by likereference characters, and first considering the furnace II andassociated electrodes I2 and I3, illustrated in Figures 1 and 2, it willbe seen that said furnace is mounted on structural supporting means I4,and provided with an oil burner I5 -for directing heat on the top of theglass, here shown as molten, and indicated by the reference characterI6. indicated at I1, and said aperture is, in the present embodiment,shown lined with a die I8 preferably formed of an alloy of platinum andrhodium, such as described and claimed in the Richardson Patent No.2,190,296, dated February 13, 1940, and owned by the assignee of thepresent application and Baker and Company, Inc.

The temperature of the glass stream I9 issuing from the furnace, isdesirably maintained uniform by sighting a radiation pyrometer 2Ithereon and controlling the heat of the furnace by means of apparatussuch as described and claimed in Patent No. 2,116,450 previouslyreferred to, so that accurately controlled amounts of glass may be fedto each lamp base 22, or other receiving device, as it passesthereunder.

In order to maintain the level of the glass in the furnace approximatelyuniform, and prevent the relatively wide variations, from a normal orpredetermined elevation within a predetermined permitted range ofvariation, which previously occurred when such furnaces were hand fed,the electrodes I2 and I3 are connected to control apparatus 23 by meansof lines 24 and 25, whereby the operation of the charging mechanism,generally designated as 26, is controlled. The electrode I2 ispreferably of special construction, such as shown in Figure 2, andcomprises a hollow preferably generally cylindrical stainless steel (18%Ni, 8% Cr), contact member 21, the lower portion of which isfrustoconical or tapered, as indicated at 28, and the lower fiat surfaceand part of the frustoconical portion covered by a cap 29 of exceedinglydurable material, preferably pure platinum .020" thick. The cap maycompletely cover the bottom and extend approximately one-half inch upthe side, being secured to the frustoconical portion 28 by crimping thetop edge portion 3| into a corresponding groove 32 in the electrode. Theuse of a platinum cap prevents the formation of high resistance scaleand the tapering to a relatively small bottom area decreases the size ofthe glass teat formed as contact is broken with the liquid surface,thereby decreasing the level change The bottom of the furnace isapertured, as

4 necessary to make and break contact with the glass.

Undesired oxidation and other deterioration of the electrode isdesirably prevented by circulation of water into connecting stainlesssteel pipe 33 and out of connecting stainless steel pipe 34.

The modified form of electrode I2a shown in Figure 3 comprises a hollow,preferably generally cylindrical stainless steel contact member 21, thelower portion of which is frustoconical or tapered, as in the form ofFigure 2, as indicated at 28. The lower nat surface in the presentinstance, however, is provided with a downwardly opening aperture inwhich is fitted a platinum button 29", instead of a platinum cap as inthe first embodiment.

As a further alternative, the hollow contact member may be made entirelyof pure nickel instead of stainless steel, with no platinum cap orbutton employed.

The other electrode I3, being entirely covered with glass and therebyprevented from substantial oxidation, need not be water-cooled. It isdesirably formed of stainless steel pipe with a piece of cold rolledsteel inside. As an alternative, a piece of cold rolled steel rod may beused. By employing electrodes of different materials, that is, in thisinstance cold rolled steel and stainless steel, a decrease occurs in theresistance of the glass when the water-cooled electrode engagestherewith. In other words, with the preferred arrangement described,resistance through the glass between the electrodes, is approximately 3ohms, whereas without the arrangement, as when a solid stainless steelbar is used with a stainless steel water-cooled electrode, theresistance would be several times such a figure. These electrodes shouldbe positioned at opposite sides of the furnace and somewhat remote fromthe charging inlet and oil burner, which latter may be disposed directlyacross from each other. The water-cooled electrode is shown protected bybeing disposed in a niche 35 in a wall of the furnace.

A desirable arrangement of the oil burner and electrodes is to positionthe former at one side of the furnace midway between the ends. Thewater-cooled electrode I2 is then positioned approximately midwaybetween one of the ends and oil burner, and the other electrode I3disposed directly opposite the water-cooled electrode. The die I8 may bedisposed near one corner, as the front left-hand corner, as viewed inFigure 1.

The charging apparatus 26 and associated driving unit 36, shown inFigures 1, 4, 5, 6 and '7,y

are desirably carried on structural framing 40 provided with wheels 31to allow for movement to and from one furnace or another as desired. Thedriving unit 36 may include a variable speed motor 3B to drive a screwconveyor 39, housed in the bottom of raw material bin 4I and cylindricalprojection 42 therefrom, through gear train in box 43, pulley orsprocket wheel 44, belt or sprocket chain 45, pulley or sprocket wheel46, jack shaft 41, pulley or sprocket wheel 48. belt or sprocket chain49, and pulley or sprocket wheel 5I xedly mounted on conveyor shaft 52,in turn carried by bearings 53 and 54. The inner end of the conveyorscrew 39, may be journalled or guided in cylindrical projecting portion42 which, in turn, fits a preferably watercooled header 55 mounted in awall of the furnace II. It will, therefore, be seen that turning of theconveyor screw in the proper direcvartesano? tion feeds raw material Ilfrom the bin 4| into the furnace II.

The top portion of the bin is desirably apertured, as indicated at 51.and a motor-driven blower or fan 59 so mounted with respect thereto thata pressure is maintained above the raw material in the bin, neutralizingor slightly exceeding the pressure in the glass furnace, which may be ashigh as 4% ofwater.

In order to maintain this pressure. the bin is normally closed byadust-tight sliding door 59. The door 59 is so mounted and operated by aspring 60 that it stays closed, because of the weight of thecable-carried abutment member 54. The associated hoist 6 I, is raisedand lowered by means of reversible hoist motor 15, associated gears 16,and cable 11, and carries a batch box 62. When they reach theintermediate position shown in Figure 5, theassociated operatorsplatform- 63 engages said abutment member 64 and starts to raise it,thereby moving the cable 55 passing over pulleys 55 and 51, between saidmember and door, and causing said door to descend to the positionillustrated in Figure 6. This makes it possible for the operator 84 topush the batch box, which has then reached its upper position, from theroller bottom 59 of the hoist 6| along the roller bottom 58 over the rawmaterial 58.

Inasmuch as the batch box desirably holds as much material as the bin,and it is not desired to let the bin get too low, said box may beintroduced when the bin is only half empty. For that reason, and for theadditional reason that it is not desired to dump the batch box when thedoor is open because it is a dust-raising operation, said box has dropdoors 50'in the bottom thereof, held closed by cables 12 and 13 wound upon a shaft carrying a ratchet 1| controlled by a pawl 10, elongated sothat its end extends beyond the batch box to provide an opeartinghandle. When the batch box is properly positioned, as illustrated inFigure 6, the handle of the pawl extends to the left such a distancethat, upon disengagement with the cable-carriel abutment member 64 whenthe operator 84 causes the hoist to descend, the door 59 trips the pawl10 and releases the ratchet 1| and drop doors 50, as it returnsI toclosed position.

The batch box is left in the position shown in Figure 6 until someconvenient time after it is emptied, whereupon the operator raises thehoist to the position shown in Figure 6 and pulls the batch box fromthe'full to dotted line position shown in said figure, and winds up theratchet shaft 14 to close the drop doors 50 and thereby place the batchbox 62 in condition for reloading.

'I'he operators platform 83 slides along the outside of the supportingframe work 80 and carries a gate 18 controlling a switch 90 and rightand left hand push buttons 19 and 8|, the functions of which will bedescribed in connection with the wiring diagram. The platform 63 is soarranged with regard to the hoist 6 I, that it does not start to riseimmediately but only upon the hoist reaching the position shown inFigure 4, where lug means 82'thereon engage corresponding lug means 83on said platform to move the latter therealong, whereby when theuppermost position, illustrated in Figure 6, is reached, the operator 84will be at the proper elevation to push the batch box from the dotted tothe full line position, or remove the same from the full to the dottedline position, illustrated, as by means of an operating pole 05.

The conveyor screw 89 may be operated continuously, the driving motor 99being run slow enough so that overcharging does not result. However, wehave found it more desirable to operate it intermittently, as byallowing the conveyor to operate a proportion of every five-minuteinterval, depending on the rate of the withdrawal of glass from thefurnace.

In order to accurately set the proportion of each five-minute intervalduring which the conveyor will operate when the electrode circuit issuch that charging is called for, we have ,pro-

vided a Icycle control or interval timer |00 of heavy duty construction,suitable for hard usagey twenty-four hours per day without attention.which timer is easily and quickly adjustable for various time cycles,reference being had to Figures 8, 9 and 10.

The timer |00, illustrated in these figures, comprises a synchronousgear-head motor 08 with an outside gear train comprising spur pinion 81,gear wheel 88, jack shaft 89, spur pinion 9|, and gear wheel 92, fixedon drive shaft 93, as by set screw IIO. Mounted on the drive shaft 93and sleeve or loose bushing 99, respectively, are disks 94 and 95,preferably formed of bakelite or other suitable insulating material, andhaving raised portions or high dwells 95 and 91, respectively, extendingaround the circumference of each. The sleeve 99 is journalled in thetimer panel ||5, desirably formed of bakelite or other suitablematerial, and the shaft 93 is journalled in the sleeve. The disk 94 isfastened to the shaft 93 as by set screw 98, while the disk 95 isfastened to the sleeve 99 as by set screw |0I.

The interval timer |00 of the present embodiment, also has a small dial|02 keyed to the shaft 93, as indicated at |03, but longitudinallymovable thereon, and a large dial I 04 carrying a vernier |05cooperating with the graduations or scale |06 on the small dial |02. Aknurled nut |01 threaded to a portion |08 of reduced diameter, extendingfrom the shaft 93, serves to frictionally clamp the small and largedials together in adjusted relationship, it being understood that thezero on the vernier can be set to register with any point on the smalldial scale. On account of the disk 95 being fixed to the same sleeve 99as the dial |04, any movement of this large dial also moves the disk.The disk 94 is thus positively driven while the disk 95 is frictionallydriven therewith. Therefore, the setting as read from the small dial isthe exact setting of the Bakelite disks, which, in turn, governs thetime the associated contacts |09 and III are closed.

The contact is carried by a spring member ||2, provided with a dependingroller II3, which rides on the disks 94 and 95 as they are turned by themotor 86, thereby separating and causing engagement of the contacts |09and III, as desired, in accordance with the setting. The motor 96 in the'present embodiment is timed so that one revolution of the disks is madeevery ve minutes.

The disks 94 and 95 can be so set that raw material is fed to thefurnace for periods of time ranging between zero and 21/2 minutes ofeach of these five-minute cycles. In actual operation the cycle controlruns continually twenty-four hours a day from Monday tov Friday, whilethe furnace is operated. It is desirably set to feed more glass than isdrawn out of the furnace, so that some time during a twenty-four-hourperiod, the glass level control, including the electrodes I2 and I3,shuts oi the operation, resulting in no more raw material being fed forperiods of fteen minutes or more.

The cycle control or timing arrangement can be set so that the amount ofraw material fed into the furnace exactly equals the glass drawn out ofit, and as long as this balance is maintained the glass level control isnot necessary. The charging apparatus has sheen run in this manner witha visual check on the glass level every eight hours and compensatingadjustments made to maintain a fairly uniform glass level.

i As examples or how the timer may be adjusted, when the vernier is setto register with the zero on the small dial, the 180 high dwellssupplement one another, so that the contacts |09 and are always heldapart and do not engage during the cycle. If the zero on the Vernier isset to register with 40 on the small dial, the contacts are closed forx/ of a revolution, or for one minute each cycle, and at 80 the contactsare closed for two minutes each cycle. This is, of course, on theassumption that the small dial is graduated 100 divisions for 180uthereof. After the desired setting is made, the knurled nut |01 istightened clamping the dials together, so that both dials rotate withthe main shaft, making one revolution in a short time interval, such asfive minutes. The entire timer is desirably enclosed in a metal box, adoor |I4 in the front exposing when open the front of the bakelite panelII5 and the dials.

The outstanding features of this interval timer or control unit are:

(l) It is rugged and will Stand up for a long period of time, even whenoperated continuously. 2) It is simple in operation and low in cost.

(3) Timing or setting of the contacts can be easily and quickly madewith no exposure to electrical wiring.

(4) The setting of the contacts can be readily ascertained by looking atthe dials.

Although we have stated that a preferred cycle is iive minutes, it willbe understood that an desired period of time may be selected by merelychanging the gear ratio or speed of operation of the shaft 93. It willalso be understood that another contact device, such as a mercuryswitch, may be substituted for the plain metal contacts |09 and III, andthat other graduations besides 100 per 180 may be employed.

Electrical control diagram Referring now to Figure l1, which is a wiringdiagram of the apparatus for the electrical control of the glass furnacelevel, we iind that the electrodes I2 and I3 are connected to thesecondary winding I I6 of a transformer ||1 through resistance I I8 bymeans of lines 24 and 25. The primary winding IIS of the transformer |I1is energized in this instance from three-phase cycle, 220 volt A. C.supply lines I2I, |22 and |23, which are connected to the circuits ofthe figure under consideration through main switch |24. The transformerprimary I I9 is shown connected to the branch lines |25 and |26, throughoverload release safety switch |21 and lines |28 and When heat issupplied to the furnace II, let it be assumed that the glass level isout of contact with the electrode I2, as illustrated. Let us also assumethat the furnace temperature is between 2500 and 2100J F. above theglass. At this temperature the gases inside the furnace are fairly goodconductors and the glass, which probably reaches a temperature of 2350F. is an excellent conductor.

Now by connecting the secondary winding II., desirably supplying 6volts, and resistance III, desirably about 200 ohms. across theelectrodes as shown, control may be obtained, as by the connectionsillustrated, with the thyratron |3I, which may be a glow tube, the RadioCorporation of America designation of which is KU636. The control is inaccordance with the resistance of the gases between the bottom of theelectrode and the top of the molten glass. plus the resistance of themolten glass between the electrodes I2 and I3.

As the gap between the electrodes and glass becomes less, as whencharging at an unnecessarily fast rate, for example, the resistancebecomes less and less until the molten glass touches the electrode I2.At the instant of contact the resistance drops to say approximately 116of that at which it might have had before the contact was made.

This variation in resistance shows that we have several means of controlincluding:

To have the bottom oi the electrode I2 at the top of the desired normallevel height range and use the make-and-break resistance changes as ameans of control.

In accordance with the diagram of Figure 11, it will be seen that we usethe procedure outlined above, because the variation in resistance isgreater and thus the control is more easily obtained.

In order to activate the tube I3I for starting and stopping the chargingmechanism 26. the grid |32 of said tube is adjustably connected to theresistance II8 through another resistance |33, of desirably about 2500ohms.

The filament |34 of the tube |3| is desirably energized bytwo-and-one-half volt secondary winding |35 of transformer II1 and thecircuit to the plate |35 by 110 volt secondary winding |31, throughresistance |38, desirably of about ohms, and relay solenoid |39 whichmay be adapted for operation at 50 volts. 'I'he solenoid |39 operates anarmature |4| to open the circuit through the solenoid |42 of the linestarter to the conveyor screw motor 39 when the level of the glass I6reaches such a height that the electrode I2 is engaged and suflicientcurrent passes through the resistance I I8 to reduce the negative biason the grid |32 suiciently to allow enough discharge to take placethrough the tube |3| to energize the solenoid |39 and draw the armatureI4I from its contact with line |46.

It will be understood that when the solenoid |42 of the line starter |43is energized, the latter closes its contacts and current passes to theconveyor screw motor 39 through lines |25, |26 and |44, protected by theoverload release safety switch |21 in circuit therewith.

The circuit to the line starter solenoid |42 Is from line |25 throughlines |28 and |45, armature |4I, line |46, timer contacts I|| and |09,and line |41 through solenoid |42 to line |44.

It will, of course, be understood that even when the armature |4| isreleased to close the circuit just outlined. as when the glass leveldrops to break contact with the electrode I2, thereby causing thenegative bias on the grid |32 to be such that the tube I 3| blocks anddoes not permit suilicient plate current to pass through the solenoid|39 to hold up said armature, the conveyor screw motor is only operatedwhen the timer disks 94 and 95 allow the roller |I3 to drop to the lowdwell |48 provided by the adjustment of said disks as shown in Figure11, to thereby permit engagement of the contacts |89 and ill. If, forany reason, it is desired to cut out the electrode control of thecharging motor 38, the switch |49 may be closed and the furnace willthen contlnuecharging under the control of only the timing device |00,the continually running motor 86 of which takes power through branchesfrom the lines |25, |26 and |44.

The hoist 6| for the batch box 62 is operated from the same power linesthrough branches I I, |52 and |53, overload release safety Aswitch |54,and reversing line starter |55, from which the direct lines |56, |51 and|58 to the hoist motor emerge. The hoist motor is controlled primarilyby selector switch |59, which determines whether it raises or lowers thehoist 6|, as by moving it to the right or the left. no opera-H011,however, being permitted until the operator 84 gets on the platform 63,closes the gate 18 thereof to thereby close the gate switch 90, and thenpushes both the left and right hand buttons 19 and 9i to effect acomplete closure of the circuit to the motor.

If the operator moves the switch to the right from the positionillustrated, the circuit is completedto the right hand solenoid |65,closing only the three right hand contacts to causo the hoist motor tooperate and lift the hoist until the latter reaches the top of itstravel when the up limit switch" |64 is opened, thereby breaking thecircuit to the solenoid |65 and stopping the hoist motor. If, for anyreason, the up limit switch fails to work, the top safety limit switch|66, immediately thereabove, would be opened, effectively breaking thecircuit to the solenoid |65.

When the operator desires to cause the hoist to I descend, he moves theselector switch to the posi- .tion at the left illustrated, the gateswitch 90 being closed and the push buttons 19 and 8| depressed,whereupon the left hand solenoid |61 is energized, closing only thethree left hand contacts of the line starter |55 and causing the hoistto descend until it opens the down limit switch |68, breaking thecircuit to the solenoid |61 and causing the contacts to open and stopthe motor.

The motor |69 of the fan or blower 58 is operated from the power linesI2I, |22 and |23, through lines |12, 13 and |14, and line starter |1|.It will be noted that the line starter solenoid |15 is always energizedby a circuit from the lines |13 and |14, except when the sliding door 59descends and opens the contact |16, thereby de-energizing the solenoid|15 and stopping the fan or blower 58, as is desired, when the door |59is open for charging the bin 4|. A red lamp |11 is desirably energizedfrom lines |13 and |14 when the fan motor is in operation. Ade-energization of said lamp indicates to the operator that the fan hasstopped, as when the switch |16 is opened by the sliding door droppingtherebeneath.

From the foregoing it will be seen that we have devised apparatus whichautomatically causes a charging screw 39 to intermittently operate inaccordance with the setting of the timer |00, and feed raw material intothe furnace until the glass level is such that the electrode I2 isengaged, resulting in energization of the solenoid |39 and a withdrawalof the armature |4| to break the circuit to the line starter solenoid|42, stopping the conveyor screw motor until the level again drops tojust break contact with said electrode, which may therefore beconsidered as the lower limit of the normal level height range. The term"normal level thus means a level within the range between and includingthat level at which the electrode I2 contacted by the glass on rising,and thatvhich the glass breaks contact with said elec rode on falling.This dropping again de-energizes the solenoid |39, causing the armature|4| to again close the circuit and allow re-energization of the conveyorscrew motor, as provided by the timing mechanism |00.

When the raw material in the bin 4| becomes so depleted thatreplenishment is necessary, an operator gets on the platform 63 with aloaded batch box 62, closes the gate 18, moves the selector switch |59to the right, pushes the buttons 19 and 8|, and thereby eiects a raisingof the batch box 62 to the position shown in Figure 6, and opening ofthe door 59, stopping the motor |69 and its fan 58. The operator thenpushes the batch box to the position shown in full lines in said figure,where the outer end of the pawl 10 is in the line of movement of thedoor 59.

To return, the operator moves the selector switch |59 back to theposition represented in Figure 11 and pushes thebuttons 19 and 8|,whereupon the hoist motor 15 reverses and lowers the hoist 6|, operatorsplatform 63, and operator 84 thereon, first to the position shown inFigure 5 where the door 59 is again closed and the fan again put inoperation, then to the position illustrated in Figure 4, where theoperator reaches the lowermost position, and finally to the posi,- tionillustrated in Figure 1 where the hoist motor is stopped by the downlimit switch |68 being opened.

Closing of the door 59 raises or trips the pawl 10 to release theratchet 1| and allow the contents of the batch box to drop into the bin4|, as represented in Figure 6. The operator at some convenient timereturns the, hoist to the position of Figure 6, pulls the empty batchbox 62 into the hoist 6|, and descends with it to the position of Figure1.

Although a preferred embodiment of our invention has been disclosed, itwill be understood that modifications may be made within the spirit andscope of the appended claims.

We claim:

1. Apparatus for maintaining the liquid level in a furnace comprisingmeans for charging said furnace, a circuit, including a relay armaturefrom a power supply to said charging means, means for controlling thetime during which said charging means acts, comprising a pair of spacedelectrodes in said furnace, one of which is submerged in, and the otherdisposed at a higher elevation so that it alternately touches the tcpsurface of, and breaks contact with the contained liquid during furnaceoperation, said oth^r electrode comprising a hollow metal element havinga frusto-conical lower portion, the sides of which are provided withnotches, a platinum cap over the lower electrode surface with edgeportions crimped in said notches, means for introducing and withdrawingcooling liquid with respect to said electrode, a powered electricalcircuit including said electrodes and a resistor in series with some ofthe furnace-contained liquid therebetween, a grid-containing controltube, having a plate circuit, whose grid is biased by a connection withsaid resistor so that its conductivity is affected by the variation inthe current iiow in said electrode circuit, and a solenoid in the platecircuit of said tube for controlling said armature, whereby saidsolenoid is energized to raise its armature and open the power supplycircuit to Said charging means, only when the higher electrode isengaged by the liquid, and said charging means thus operates onlv whenmaterial is needed to bring the liquid level up to contact saidelectrode.

2. Apparatus for maintaining a predetermined level of liouid glass in amelting furnace comprising means for charging said furnace, a poweredcircuit for energizing said charging means, a switch in said circuit forcontrolling said charging means, means comprising a pair of motordrivencam disks rotatable with respect to one another, to provide a desiredratio between high and low dwells, and a make-and-break device operatedthereby, for adjusting the part of each of uniform time intervals duringwhich said furnace charging means operates, a first electrode submergedin said glass, a second electrode disposed above said first electrode,and a powered circuit including said electrodes, and a solenoid withsaid switch as its armatuie opened only when said solenoid is energizedupon the glass level rising to contact said second electrode to decreasethe circuit resistance and allow effective solenoid current to flow,wherebv said furnace is charged until the lif'uid therein touches saidsecond electrode anri effects a stoppage of said charging means untilthe limiid drops out of contact again with said electrode.

3. Apparatus for maintaining a predetermined level of liouid glass in a.melting furnace comprising means for charging said furnace, a firstelectric motor for driving said charging means, a pcwered circuit tosaid motor includingr a switch and a make and break device. and meansfor actuating said make and break device to control the operation ofsaid charging means, comprising a pair of cam disks adjustable withrespect to one another to provide a desired ratio between high an'i lowdwells, a second motor for driving said adiusted disks at uniform speed,so as to operate said make and break device and close the circuit tosaid first motor when the one dwell engages the same and open it whenthe other dwell is in contact therewith, an electrode contacting saidglass and another electrode with its lower end extending down to a levelabove which the glass should not rise. to any extent, a powered circuitincluding said electrodes and a solenoid with said switch as itsarmature opened only when said solenoid is energized upon the glasslevel rising to contact said second-mentioned electrode to decrease thecircuit resistance and allow effective solenoid current to flow so thatthe charging means motor stops when the glass level engages said secondmentioned electrode and restarts when the glass drops out of contacttherewith.

4. In combination with a glass-melting furnace. a raw material bin, ahollow cylindrical projection tube from said bin to said furnace. aconveyor screw in said tube, electrical power means for turning saidscrew to feed material from said bin out of said tube and into saidfurnace to provide an accumulation of molten glass therein, a powercircuit to said feeding means and means for controlling the operation ofsaid feeding means comprising a pair of cam disks adjustable withrespect to one another to provide a desired ratio between high and lowdwells, a motor for rotating said adjusted disks at uniform speed, amake-and-break device in said circuit and operated by said disks so asto close said circuit when one dwell engages the same and open it whenthe other dwell is in contact therewith, an electrode normallycontacting said accumulation and another electrode with its lower endextending over said accumulation to a level above which saidaccumulation should not rise, a source of electric current in a circuitthrough said electrodes, the molten glass therebetween and a seriesresistor, a grid-controlled tube energized from another source, aconnection between said resistor and the grid of said tube, so that adischarge occurs through the latter when the circuit current is high,and stops when it is reduced below a Dredetermined value, a solenoidconnected to receive the discharge current from said tube, and anamature to said solenoid in said make-and-break device circuit, so thatthe solenoid pulls its armature and opens the circuit to said powermeans, when said accumulation engages said secondmentioned electrode,and keeps it open until it drops out of contact therewith.

5. Apparatus for maintaining the liquid level in a melting furnacecomprising, charging means, a circuit including a relav armature from apower supply to said charging means, a. pair of electrodes in saidfurnace disposed so that some of said liquid is therebetween, one ofsaid electrodes being at a relatively low elevation so as to be alwayscontacted by said liouid the other electrode being at a higher elevationso as to be contacted only after the liouid reaches a predeterminednormal level, a second powered circuit incuding said electrodes and asolenoid controlling sad relay armature, said solenoid being therebyenergized to move said armature and open said first circuit when theliquid rises until it reaches said higher electrode, thereby decreasingthe resistance in the second circuit and effecting an increase in thecurrent therein, and timing mec`nanism including a pair of cam disks,one of which is ilxedion a sleeve and the other on a shaft journalled insaid sleeve, said disks having high dwells extending approximatelyaround their peripheries, wherebv they may be adjusted with respect toone another to leave a low dwell of any desired length i`etween 0 and180, means i'or showing the relative adiusiment of said disks comprisinga graduated dial on said shaft and another dial having a registeringzero point thereon, means for tightening said dials in adiusted positionwith respect to one another to determine the length of the low dwellmeans for turning said shaft and sleeve at a uniform predeterminedspeed, and a contact device in said chargingmeans-circuit, said deviceengaging said disks and moved thereby so that it opens and closes saidcircuit for predetermined time intervals in accordance with the speed ofshaft rotation and the cam disk adjustment, whereby said charging meansoperates only when said relatively high electrode is not contacted bysaid liquid and also during only a desired portion of the disk rotationpredetermined by the ratio between the dwells provided by saidadjustment.

6. In combination with a glass melting furnace comprising a refractoryenclosure having an aperture in a side wall thereof defined by a hollowheader, a raw material charging bin, charging means comprising a screwconveyor passing through said header for feeding raw material from saidbin to said furnace, a pair of electrodes in said furnace remotelydisposed with respect to one another, one of said electrodes being at arelatively low elevation so as to be during opera.- tion alwayscontacted by the molten glass, and the other being at a higher elevationso as to be contacted only after said glass reaches normal level, meanscontrolling the operation of said charging means comprising a pair ofcam disks 13 adjustable `with respect to one another to provide adesired ratio between high and low dwells, means for turning saidadjusteddisks, a powered circuit to said charging means, contacts insaid circuit so arranged with respect to said cam disks that they arecaused by engagement of said turning disks to engage and disengage inaccordance with the difference in elevation between said high and lowdwells, to energize and vie-energize the charging means, a relayarmature also in said charging means circuit, and a powered controlcircuit including said electrodes and -a solenoid controlling saidarmature and energized only when the higher electrode is contacted bysaid glass to open said charging means circuit, whereby said chargingmeans operates only when the level o! the glass drops so that contact isbroken with said 'higher electrode, and also. only when saidv V contactsare engaged by means of said cam disks.

7. Apparatus for Amaintaining the liquid level` ing means acts,comprising a pair of spaced electrodes in said furnace, one of which issubmerged in, and the other disposed at a higher elevation so that italternately touches the top surface of,

and breaks contact with, the contained liquid during furnace operation,a powered electrical circuit including said electrodes and a resistor.inseries with some of the furnace-contained liquid' therebetween, agrid-containing control tube.' having a plate circuit, whose grid isbiased by'a connection with said resistor so that its conductivity isaii'ected by the variation in the current now in said electrode circuit.and a solenoid in the plate circuit of said tube for controlling saidarmature, whereby said solenoid is energized to raise its armature andopen the power supply circuit to said charging means, only when thehigher electrode is engaged by the liquid, and said charging means thusoperates only when material is needed to bring the liquid level up tocontact said electrode.

JAMES B. WHII'MORE.

FRANK A. NEWCOMBE.

REFERENCES CITED The following references are of record'in the ille ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 19,788 Amsler Dec. 17, 19351,801,585 Arthur Apr. 21, 1931 1,842,919 Simmons June 26, 1932 1,867,489Bennett et al July l2, 1932 1,889,510 Amsler Nov. 29, 1932 1,924,907Bower Aug. 29, 1933 1,941,897 Hiller Jan. 2, 1934 1,961,893 Wadman etalJune 5; 1934 1,977,969 McIntosh Oct. 23, 1934 1,998,038 Wottring Apr.16, 1935 2,096,182 Kerr et al Oct. 19, 1937 2,141,024 Staley Dec. 20,1938 2,141,259 Whittaker Dec. 27. 1938 2,202,197 Ewertz May 28, 19402,234,858 Brown et al.`..- Mar. 11, 1941 2,246,375 Lyle June 17, 19412,262,070 Turk Nov. 11, 1941 2,357,371 Wolfner Sept. 5, 1944 AckermanSept. 21, 1948

